With the exception of Samuel L Jackson and Chris Evans, the cast gathered in London for the European premiere of The Avengers, which has been internationally retitled Avengers Assembled to avoid confusion with a certain vintage British TV series. It was one of those slightly over-crowded press conferences, with too many people answering too few questions. But everyone was in a great mood, even through the fog of jet lag as they traverse the globe to present the film to adoring audiences everywhere. Robert Downey Jr is clearly the father figure in this gang, although he sat back and let them speak, which is somewhat unusual for someone as naturally chatty as he is. But this allowed the sharp wit of Mark Ruffalo and Tom Hiddleston to shine. Kind of like the film itself, this felt like four press conferences crammed into one....

While working on Iron Man, was there a point when you realised you'd be taking part in a series of Avengers movies?
Robert Downey Jr: From five years ago when we did the first Iron Man to today with all these folks you see up here, it couldn't have gone any better. All three franchises that we've launched so far had to work, and if this didn't work it would affect all the previous franchises extremely adversely. And there's also the potential for additional franchises based on how strongly people are reacting to Jeremy, Scarlett and Mark. So I really don't understand how everything has gone this well, but in this one instance in my life that seems to be the situation.

How did Joss Whedon manage to get all of these characters into one film, and giving them all decent screen-time?
Tom Hiddleston: The thing that was most impressive to me about Joss initially is the incredible screenplay that he wrote. I mean, as an achievement in itself as a filmmaker, his screenplay was simply phenomenal because I think that all of us weren't sure what to expect. It was extraordinary, and I take my hat off to him, because I think that was his hardest job. It must have made directing it seem like a walk in the park. Well, maybe not a walk in the park. Maybe a light jog.

Throwing myself on the floor repeatedly, I must have looked like a lunatic.

What was your favourite fight move and why?
Mark Ruffalo: [shrugs] There's so many! I'm Bruce right now.
Chris Hemsworth: My favourite fight move was when you [Hulk] slammed Loki repeatedly back and forth.
Ruffalo: That's kind of my favourite too. And it's Loki's favourite as well!
Hiddleston: It is actually. Partly because some strange small person called Tom had to do most of that himself too. Hurling myself into the air and throwing myself on the floor repeatedly, I must have looked like a lunatic, which kind of describes Loki quite adequately.
Downey: My favourite move or Tony's favourite move? Well you know, probably how I can fall out of buildings and survive because of my tech! You notice that fight move involves no one but me and my stuff?
Hemsworth: For me it's probably the summoning of the lightning and the cracking on the ground and the ripple effect that it has on the earth, which we didn't do in this movie but we did in Thor. Maybe in Thor 2 I'll get to do it again.
Scarlett Johansson: My favourite fight move - or Natasha's favourite fight move - is probably the thigh grip. What's it called? The thigh-master hold!
Jeremy Renner: To be choked out by your thighs would be a good way to go.
Downey: That's my favourite move too.

Joss Whedon is well-known for creating strong female characters.
Johansson: Joss met with each of us individually to talk about what we wanted to see from our characters and we did talk about my character's plight, her dark past and all of those things. But never once did he say anything about my character's gender at all, and we never talked about it. I think that's a perfect example: Joss is gender-blind. He wants his female characters to be dynamic, competitive, assured and confident. And that has nothing do with anything but the fact that he just celebrates those kinds of strong female characters. He's a charming fellow that way.

How much input did you have in creating your character?
Hiddleston: Joss was incredibly open, and that is really all that you want as an actor. You want to collaborate. Everybody has a degree of ownership about the characters they play, and he's very respectful of that possession. He's also respectful that we've all lived under the skins of our characters for some time. So he was constantly asking "Does this feel right?" "Does this feel true to you?" "Is this in your voice?" But most of the time I was just turning up and saying my very brilliant lines which he had written on my behalf.

I love getting to bust out into the big green rage machine.

Mark, what attracted you to the role of Dr Banner?
Ruffalo: As a kid I was a Hulk fan, and I was particularly fan of the TV show. So when I was offered the Hulk, or Banner, I talked to Joss Whedon about it. And he said he wanted to return to the Bill Bixby kind of world-weary charm of a man who is on the run but still trying take time to live his life and falling in love and having a sense of humour about himself and I like that. I also liked the idea that I would be the first actor to play both Banner and the Hulk. That was probably the most exciting thing to me. Technology has brought us to a place where an actor can play the Hulk. I love Joss' take on the world-weary charm, but I also love the idea of actually getting to bust out into the big green rage machine.

And what was that process?
Ruffalo: It was motion capture. Yes, there was the element of wearing a leotard that reduced me to a Chinese checker board, but other than that it was a very involved three-part process: we did all the motion capture before we shot the movie, we did it while we were shooting the movie and we did it after. It was a very very intensive process and I was by myself most of the time, which was lonely. In a leotard that makes all the wrong places look big and all the right places look small.

Jeremy and Scarlett, was it a challenge to play the two Avengers without superpowers? Which of your team's abilities would you want?
Johansson: Jeremy and I - and Tom - probably spent the most amount of time in the stunt gym, because we have these huge choreographed sequences that are just, you know, intense. As characters and as actors in this film, it's our burden to bear. But I'm happy to do that. We have such an amazing stunt team, and I knew a lot of them from Iron Man 2. We spent so much time in the stunt gym that we built a family with those guys. And it's great fun to do it. But I don't want superpowers.
Renner: I don't want any superpowers either.
Johansson: Yeah we decided that we would rather be skilled because your superpowers may disappear.
Renner: Sure. If Thor lost his hammer, he'd still kick my ass, but at least I'd have a fighting chance. I still have a skill set.
Hemsworth: I thought the fight scene between you guys was one of the most satisfying because it was grounded in the most reality: this incredible choreographed hand-to-hand sequence, which was hugely impressive.
Johansson: Thanks.
Hemsworth: No worries!

Mark, did you worry about taking over as Bruce Banner, especially with all the fanboy rumbling out there?
Ruffalo: I was overcome by a moment of very poor judgement early on, by going online and seeing the response to me stepping in as the new Banner. I won't do that again! It wasn't glowing. And I found the fans' exuberant passion to be very very brutal. I hope we've amended that.
Hiddleston: One of the strange things about being in these films is that we're lucky enough to have a fan base. I mean it's so often that you make a film and you put your heart and soul into it, you really care about it and you think it's half-decent. And wonder, "Does anyone want to see it?" And maybe nobody does. But we're lucky that we already have people who love the characters as much if not more than we do. And I find it thrilling that there's a pre-existing passion for the material in a way. It's such a privilege actually, it really is, to have people that care that much. Rather than being paralysed by a fear of what they might think, it's a challenge to deliver what you hope they might enjoy.